Properties of soft Bangkok clay stabilized with cement and fly ash geopolymer for deep mixing application

Deep mixing (DM) is a technique for improving the ground that has been widely used worldwide. Ordinary Portland cement (C) has historically been the most popular binder for DM application; however, utilizing C releases a large carbon footprint. This research investigates the properties of soft Bangkok clay (SC) stabilized with C and high calcium fly ash (FA) geopolymer for highstrength soil-cement columns. The effect of influence parameters on the unconfined compressive strength (UCS) and scanning electron microscope (SEM) properties of SC-C-FA geopolymer specimens was measured. The specimens had initial water contents (w) of 1LL, 1.5LL, and 2LL, FA:C ratios ranged from 100:0-70:30, and sodium silicate:sodium hydroxide ratios (NS:NH) of 50:50, 70:30, and 80:20. The results indicated that the UCS of SC-C-FA geopolymer specimens was found to increase with the increasing C content. Whereas, the UCS decreased with the decreasing NS:NH ratios. The highest 28-day UCS of the specimen was obtained with initial water content of 1.5LL, FA:C ratio of 70:30, and NS:NH ratio of 50:50. The 28-day UCSs of SC-C-FA geopolymer with all initial water contents, C content greater than 5%, and NS:NH ratio of 50:50 passed the minimum UCS requirement for soil-cement columns. Furthermore, the equations for predicting UCS and carbon emissions of SC-C-FA geopolymer are very useful for designing soil-cement columns.